I understand the domain and range. What i don't get is, the product of squaring any number would give me two answer so f(g(x)) wouldn't be a function. ex: if i square 4 wouldn't i get + or - 2.

no, if you square 4 you get 16. what you are getting at is the square-root of 4. in that case the answer is 2. only 2, -2 is not . since for all

definitions that always seem to help me:

the domain is the set of input values (in this case, x values) for which a function is defined, or has an output value.

the range is the set of output values (in this case, y-values)

so just figure out what x-values work in your function, and that's your domain. it is often easier to find what does not work, and say the domain is the set of all values but those that don't work. the range is the set of outputs you can obtain by plugging in any one of these domain values